Method and apparatus for making granular coated webs



.Aug. 4, 1936.

R. c. BENNER ET AL 2,049,535 METHOD AND APPARATUS FOR MAKING GRANULAR COATED WEBS Filed Dec. 1, 1932 INVENTOR. RAYMOND C. BENNER HENRY F! KIRGHNER 3yv WE L. MELTON A TTORNE Y Patented Aug. 4, 1936 UNITED STATES. PATENT OFFICE Raymond C. Benner, Henry P3 Romie L. Melton,

Falls, N. Y.,

Kirchner, and

Niagara Falls, N. Y., assignors to The Carborun dum Company, Niagara a corporation of Pennsylvania Application December 1, 1932, Serial No. 645,254 '1 Claims. (01. 91-13) This invention relates to an improvement in the manufacture of granular coated products, such as abrasive coated webs of paper, cloth and the like. More specifically, the invention is concerned with that part of such a process wherein a layer of adhesive is applied to a backing material preliminary to the attaching of granular particles to said backing.

The present invention relates primarily to a method and apparatus or controlling the viscosity of a layer of adilesive, after it is applied to a web, and convertir" and/or maintaining said adhesive coating in a suitably fluid condition for the retention of granules deposited thereon.

In the manufacture of granular coated webs, a layer of adhesive is applied to one side of the web by some suitable means, such as by transferring it by means of a roll immersed in the liquid adhesive. The granular material is then applied to the adhesive coated side of the web, following which the adhesive is hardened, as for example, by cooling and drying, where a glue is used, or by evaporating the solvent where the adhesive is in the form of a solution of the adhesive in a relatively volatile solvent.

Considerable difiiculty has been experienced in certain modifications of this process because of the fact that certain adhesives set or harden before the granular materials can be applied. This difliculty is particularly pronounced in certain types of apparatus in which there is an appreciable distance between the adhesive applying device and the grain depositing means.

We have found that this difliculty can be obviated by subjecting the adhesive coated fabric to the action of an atmosphere maintained at such a temperature and vapor pressure of the solvent that the adhesive is in a satisfactory condition for the reception of the granular material. This is most conveniently done by passing the adhesive coated fabric through a chamber having a controlled atmosphere.

A better understanding of the process and apparatus may be obtained by reference to the accompanying drawing, in which:

Figure 1 is a diagrammatic side elevation of one type of granular coating apparatus embodying our invention;

Figure 2 illustrates another type of apparatus; and

Figure 3 illustrates still another type of coating apparatus.

In Figure 1, the web -P passes over the idler rolls 2, 3, and 4 and between the adhesive roll 5 and the backing roll 6 whereupon a coating of adhesive is applied from roll 5 which is partially immersed in the adhesive contained in the pan 1. Upon passing from the backing roll 6, the web enters the chamber A in which the atmosphere is maintained at such conditions of temperature and humidity (where glue is the adhesive) that the glue is of a suitable consistency to receive the granular material as it leaves the chamber. The temperature of the atmosphere is w controlled by the heating elements I I, which may, for example, be steam pipes 'or electrical heating units, while humidity is controlled by the admission or introduction of water vapor. Circulation of the atmosphere is maintained by a fan l4 driven externally by means not shown in the drawing. Supporting rolls 9, l0, and la maintain the fabric in a suitable position as it is drawn through the apparatus by the suction drum 30. Upon leaving the chamber A the granular material is projected upward onto the adhesive from the belt l9 by reason of the oscillations set up in a portion of the belt by the rotating heaters 23. Granules, which do not adhere to the adhesive surface, fall back onto the belt and are carried into the bin 25. Granular material is dispensed to the belt from the hopper l5, suitably supplied with a gate l6 and a feed roll H. The belt I9 is suitably drivenand supported by the pulleys 20, 2|, and 22.

Figure 2 represents a similar type of apparatus suitable for use where the granular material is to be dropped onto the upper side of an adhesive coated web. In this form of our invention the adhesive is applied and kept in the proper condition of viscosity as described in connection with the preceding example. The granular material is fed, as described above, from the feed hopper IE but in this case drops directly onto the adhesive coated web.

Figure 3 represents another form of our invention in which the adhesive is applied by means of automatically controlled spray nozzles 21, mounted on the supporting members 28. In this embodiment, which is particularly well adapted for use where the adhesive is applied in the form of a solution in a relatively volatile solvent, the vapor pressure of the solvent in the chamber B is maintained at the desired value by reasonof the evaporation of solvent from the vessel 29, which maybe assisted and controlled by supplying heat through the elements 30. The atmosphere of the chamber may be further heated by elements 3| if desired. Reference numeral 32 represents a drain for removing excess solvent which may condense on the walls of the chamber. Since some types of adhesives are inclined to congeal when sprayed, it is desirable to use air 5 that has been warmed and humidified with steam for operating the spray nozzles, if the adhesive is water soluble, or air laden with a solvent, if the adhesive is one such as lacquer or varnish.

Our invention has been found to be particularly advantageous in connection with processes for applying granular material wherein the grains are projected upward onto the under side of a web, one example of which is illustrated in Figure 1. Such methods of coating have been found to produce improved products by reason of the fact that irregular shaped granules, particularly those having at least one of their dimensions appreciably greater than the others, are thereby oriented on the backing in such a manner as to present an unusually sharp surface which has been described as a surface having a high index of serration". Coated webs having a surface with a high index of serration, the apparatus for and methods of producing the same, are

35 disclosed and claimed in our copending applications, Serial No. 647,241, filed Dec. 14, 1932, and Serial No. 636,982, filed October 10, 1932.

In designing machinery for such general methods of applying granular material, and particularly for the projection of granules onto the under side of adhesive coated webs, it is diflicult to position the adhesive-applying apparatus close to the grain-projecting means. Our improved method and apparatus for controlling the vis- 35 cosity of the adhesive at the place where the grain is applied has therefore been an exceedingly valuable, if not an indispensable, aid to the functioning of grain-projecting apparatus of this latter type.

40 Our invention is also advantageous in the manufacture of the ordinary glue bonded'coated products as exemplified by abrasive /paper as made by the methods heretofore known and illustrated in Figure 2.

45 In the manufacture of abrasive paper by any method, it is necessary to maintain a substantially constant relationship between the thickness of the adhesive coating which is applied to the backing and the size of the abrasive grains.

5 It has heretofore been customary, in order to accomplish this purpose, to use glues of different viscosity for different grit sizes. When fine grit products are being made, a thinner glue is made up by adding more water to the glue solution,

5 while for coarse grits, a more viscous solution is required in order to get a coating of sufficient thickness, and is secured by reducing the quantity of water in the glue. Since the temperature of a glue solution has a marked effect on the viscosity, this is also customarily regulated by supplying external heat to the glue pots.

The adjustment of viscosity by a variation in the temperature is, however, objectionable for the reason that, as is well known, glue is materially weakened when it is continuously kept at elevated temperatures. Variation in the concentration of the glue solution is also objectionable because an increase in the quantity of water 70 added means that a longer time is required for drying the glue. Our improved process permits a reduction in the magnitude of the effect of these objectionable practices and hence produces an article of better quality and greater uniformity.

Our invention has also been found to be of great value in the manufacture of granular coated webs wherein the adhesive is applied in the form of a solution in a relatively volatile solvent such as a lacquer or a varnish. In such 5' cases, the adhesive is very prone to thicken and dry out by reason of the evaporation of the solvent, particularly where it is applied in the form of a spray where the solution is necessarily very finely divided and consequently has a relal0 tively large amount of surface exposed. The provision of a solvent saturated atmosphere in such cases greatly reduces the' thickening of the adhesive and assists materially in making the process operative from a practical standpoint. 15

It is not intended that our invention should be limited to the examples given herein, which were for illustrative purposes only, but rather that the scope should be defined by the appended claims, as obviously our improvement is adaptable to 0 other processes wherein an adhesive is applied to a backing preliminary to the step of coating the backing.

We claim:

1. Apparatus for the manufacture of granular coated webs comprising means for applying liquid adhesive to a web, means whereby the partial pressure of a solvent in the atmosphere in a chamber may be controlled to prevent drying, grain applying means for applying granular particles to said adhesive coated web, and means for passing said adhesive coated web through said chamber and past said grain applying means whereby the granular material is applied to the web while the adhesive is in condition for receiving said granular material.

" 2. Apparatus for the manufacture of granular coated webs comprising means for applying liquid adhesive to a web, means whereby the tem perature and humidity of the atmosphere in a chamber may be controlled to prevent drying of said liquid adhesive, means for projecting granular particles upward and means for passing said adhesive coated web through said chamber and over said grain projecting means whereby the granular material is projected upward onto the under side of said web while the adhesive is in condition for receiving said granular material.

3. Apparatus for the manufacture of granular coated webs comprising means for applying liquid adhesive to a web, a chamber through which said adhesively coated web is passed, means whereby the atmosphere in said chamber may be controlled to prevent drying of said liquid ad- 35 hesive and means adjacent to said chamber for applying granular particles to the adhesively coated web.

4. Apparatus for the manufacture of granular coated webs comprising means for applying liquid adhesive to a moving web, means whereby the atmosphere adjacent said web may be controlled to preventdrying of the saidliquid adhesive and means for applying granular material to said adhesively coated web prior to substantial drying of said adhesive.

5. The method of manufacturing abrasive coated webs which comprises applying a layer of liquid adhesive to a web backing in proper condition for retaining abrasive grains deposited thereon, passing the adhesive coated web through a zone of controlled atmosphere to maintain the adhesive in a substantially unchanged condition and immediately thereafter applying abrasive rains to, the adhesive coated side of the web.

6. The method of manufacturing abrasive coated webs which comprises applying a layer of liquid adhesive toa web backing in proper condition for retaining abrasive grains, passing the adhesive coated web through a zone of controlled atmosphere to maintain the layer of adhesive in a substantially unchanged condition, moving the web into a position with the adhesive coated side facing downwardly and projecting abrasive particles upwardly against said downwardly facing adhesive coated web prior to an appreciable change in condition of said adhesive.

7. Apparatus for the manufacture of abrasive coated webs comprising means for applying a layer of liquid adhesive to a web backing in proper condition for retaining abrasive grains, 2. chamher through which said coated web is passed. said apparatus being adapted to control the atmosphere in said chamber to prevent a change in condition of the adhesive, means for changing the direction of movement of said web and supporting said web with the adhesive coated side facing downwardly, a feed belt adapted to carry abrasive grains into a position beneath and in close proximity to said downwardly facing adhesively coated web, means for supplying abrasive grains to said feed belt and means for projecting said abrasive grains upwardly onto said downwardly facing adhesive coated web.

RAYMOND C. BENNER. HENRY P. KmC'HNER. ROMIE L. MELTON.

DISCLAIMER 2,049,535.Raymond 0'. Banner, Henry P. Kirchner, and Romie L. lilelton, Niagara Falls, N. Y. METHOD AND Armm'ms FOR MAKING GRANULAR COATED WEBB. Patent dated August 4, 1936. Disclaimer filed February 11, 1943, by the assignee, fl'he Oarbomndum Company.

Hereby disclaims claim 1 of said patent. [Oficial Gazette March 16', 1948.] 

